[pve-devel] Default cache mode for VM hard drives

[Dietmar Maurer]

> I have just done the same test with mdadm and not DRBD. And what I found
> that this problem was reproducible on the software raid too, just as it was
> claimed by Lars Ellenberg. It means that problem is not only related to
> DRBD but to O_DIRECT mode generally when we don't use host cache and a
> block device reads data directly from userspace.

We simply think the behavior is correct. If you want to be sure data is
on disk you have to call fsync.